Method, device and computer program for primary cell change

ABSTRACT

Embodiments of the disclosure generally relate to primary cell change. A network device detects whether layer 2 context being kept and/or one or more serving secondary cells remain for a primary cell change for a terminal device. Then, the network device configures a message indicating the primary cell change based on the detecting and transmits the message to the terminal device. The time period of primary cell change can be reduced efficiently and the data transmission during the primary cell change can be optimized.

TECHNICAL FIELD

The non-limiting and example embodiments of the present disclosuregenerally relate to a technical field of wireless communications, andspecifically to a method, device and computer program for primary cellchange in a wireless communications system and related communicationdevice.

BACKGROUND

This section introduces aspects that may facilitate a betterunderstanding of the disclosure. Accordingly, the statements of thissection are to be read in this light and are not to be understood asadmissions about what is in the prior art or what is not in the priorart.

Wireless communication systems are advancing to provide good servicequality, support a high data rate and keep up with the continuouslyincreasing demand for wireless data traffic.

Multi-carrier system is a technique available for increasing thebandwidth available for communication by employing simultaneously morethan one carrier for communication by a single communication device. Amulti-carrier system uses more than one carrier in the downlink and/orthe uplink.

For bandwidth extension, carrier aggregation (CA) was introduced to theLTE-A system and it was firstly defined in 3GPP Rel-10 and by which twoor more component carriers are aggregated to achieve a wider-bandtransmission. An LTE-A specification supports carrier aggregation forboth continuous and non-continuous component carriers. The carrieraggregation increases bandwidth flexibility by aggregating thenon-continuous component carriers. A component carrier is used as an ULcomponent carrier or a downlink (DL) component carrier. Now CA is animportant feature in LTE which can improve both system capacity and UserEquipment (UE) performance. When the UE is configured with the carrieraggregation, the UE is allowed to receive and transmit data on one ormultiple component carriers to increase the data rate. In the LTE-Asystem, it is possible for the eNB to configure the UE different numbersof UL and DL component carriers which depend on UL and DL aggregationcapabilities, respectively.

Moreover, the component carriers configured to the UE necessarilyconsists of one DL primary component carrier (PCC) and one UL primarycomponent carrier. Component carriers other than the primary componentcarriers are named UL or DL secondary component carriers (SCCs). Thenumbers of UL and DL secondary component carriers are arbitrary, and arerelated to the UE capability and available radio resource. One of theserving cells is designated as a “primary cell”. A serving cell that isnot a primary cell is referred to as a secondary cell. The functionsprovided by the primary cell include being responsible for many controlplane related events, e.g. providing the necessary information for NAS,e.g. TAI, providing input for security, determining RLF, being thereference Carrier to determine handover, being the carrier to carryPUCCH channel etc.

When the communication link between the UE and the primary cell on thePCC is interrupted, the communication between the UE and the networkfails even if the communication link between the UE and a secondary cellis sustained. Given the importance of the link between the UE and theprimary cell considering the functions provided by the primary cell, inorder to minimize problems associated with radio link quality and otherissues, it is necessary to ensure that the primary cell is the best cellof the serving cells in terms of quality. Such a requirement then makesit necessary to change the primary cell when the current primary cell isno longer the best cell in radio link quality. According to 3GPP Rel-13,primary cell can only be changed with handover procedure (i.e. withsecurity key change and RACH procedure).

SUMMARY

The above requirement of 3GPP Rel-13 may result in some undesirableeffects during primary cell change for the next generation networks.When primary cell needs to be changed, a handover procedure is neededwhich means RRCConnectionReconfiguration message includingMobiltyControlInfo is sent to UE, which will then trigger PDCP/RLCreestablishment, MAC reset, new key derivation, and random accessprocedure at a new primary component carrier. Usually this procedurewill take around 40 ms, and during this period, data transmission isinterrupted. Moreover, in the next generation networks such as NR, dueto high frequency band and beamforming used, the primary cell changecould be more frequent than in LTE and such a long time period of datainterruption during the primary cell change is undesirable.

In order to solve at least part of the above problems, methods, devicesand computer programs are provided in the present disclosure. It can beappreciated that embodiments of the present disclosure are not limitedto a wireless system operating in NR network, but could be more widelyapplied to any application scenario where similar problems exist.

Various embodiments of the present disclosure mainly aim at providingmethods, devices and computer programs for controlling a transmissionbetween a transmitter and a receiver, for example, in a shared frequencyband. Each of the transmitter and the receiver could be, for example, anetwork device or a terminal device. Other features and advantages ofembodiments of the present disclosure will also be understood from thefollowing description of specific embodiments when read in conjunctionwith the accompanying drawings, which illustrate, by way of example, theprinciples of embodiments of the present disclosure.

In a first aspect of the disclosure, there is provided a methodimplemented at a network device. The method includes: detecting whetherlayer 2 context being kept and/or one or more serving secondary cellsremain for a primary cell change for a terminal device; configuring amessage indicating the primary cell change based on the detecting; andtransmitting the message to the terminal device.

In one embodiment, detecting whether layer 2 context being kept for aprimary cell change for a terminal device is detecting whether part orentire of the layer 2 context corresponding to a second primary cellkeeps the same comparing to a first primary cell; and/or detecting oneor more serving secondary cells remain for a primary cell change for aterminal device is detecting whether index of the second primary cell issame as one secondary cell of a first group of secondary cells; theterminal device is being served by the first primary cell and the firstgroup of secondary cells, and to be severed by the second primary celland a second group of secondary cells after the primary cell change.

In one embodiment, the method further includes: in response to it beingdetected that entire of layer 2 context not being kept; configuring themessage by including at least security information element to requirethe terminal device to derive a new security key.

In one embodiment, the method further includes: in response to it beingdetected that entire of the layer 2 context except PDCP entitycorresponding to the second primary cell not being kept comparing to thefirst primary cell; configuring the message by including at leastinformation element to trigger reconfiguring of RLC/MAC entity.

In one embodiment, the method further includes: in response to it beingdetected that entire of layer 2 context being kept and the index of thesecond primary cell is not same as any secondary cell of the first groupof secondary cells; configuring the message by including at least IDinformation of the second group of secondary cells.

In one embodiment, the method further includes: in response to it beingdetected that the index of the second primary cell is same as onesecondary cell of the first group of secondary cells; configuring themessage to include at least ID information of the second primary cell.

In one embodiment, the method further includes, wherein the MAC messageis transmitted in a MAC or RRC message.

In one embodiment, the method further includes, wherein the MAC messageincludes a MAC control element which is identified by a Logical ChannelID.

In one embodiment, the method further includes, wherein the MAC messageincludes a MAC control element which indicates index of the secondprimary cell.

In one embodiment, the method further includes, wherein the controlelement is transmitted via all existing component cells controlled bythe network device which continues transmitting the MAC control elementuntil receiving a HARQ ACK from one of the component cells correspondingto this MAC control element transmission.

In a second aspect of the disclosure, there is provided a networkdevice. The network device includes: a detecting unit configured todetect whether layer 2 context being kept and/or one or more servingsecondary cells remain for a primary cell change for a terminal device;a configuration unit configured to configure a message indicating aprimary cell change based on the detecting by the detecting unit; atransmitting unit configured to transmit the message to the terminaldevice.

In a third aspect of the disclosure, there is provided a methodimplemented at a mobile terminal. The method includes: receiving amessage transmitted from a network device, the message being configuredby detecting whether layer 2 context being kept and/or one or moreserving secondary cells remain for a primary cell change for theterminal device; obtaining information of the change of primary cellfrom the received message; performing the primary cell change based onthe information.

In one embodiment, detecting whether layer 2 context being kept for aprimary cell change for the terminal device is detecting whether part orentire of layer 2 context corresponding to a second primary cell keepsthe same comparing to a first primary cell; and/or detecting one or moreserving secondary cells remain for a primary cell change for a terminaldevice is detecting whether index of the second primary cell is same asone secondary cell of a first group of secondary cells or theindex(indices) of one or more of the second primary cell and secondarycells in the second group of secondary cells included in the message isthe same as the first primary cell and secondary cells in the firstgroup of secondary cells; and the terminal device is being served by thefirst primary cell and the first group of secondary cells, and to besevered by the second primary cell and a second group of secondary cellsafter the primary cell change.

In one embodiment, the method further includes: in response to it beingdetected that the received message includes an information element forderivation of a new security key; updating the second primary cell indexaccording to the received message; deriving a second security key;resetting MAC; re-establishing PDCP/RLC; and initiating random access tothe second primary cell.

In one embodiment, the method further includes: in response to it beingdetected that the received message include an information element totrigger reconfiguring of RLC/MAC; updating the second primary cell indexaccording to the received message; resetting MAC; re-establishing RLC;and initiating random access to the second primary cell.

In one embodiment, the method further includes: in response to it beingdetected that the received message does not include an informationelement for derivation of a new security key or triggering reconfiguringof RLC/MAC while the index(indices) of one or more of the second primarycell and secondary cells in the second group of secondary cells includedin the message is not the same as any of the first primary cell andsecondary cells in the first group of secondary cells, updating thesecond primary cell index according to the received message; initiatingrandom access to the second primary cell.

In one embodiment, in response to it being detected that theindex(indices) of one or more of the second primary cell and secondarycells in the second group of secondary cells included in the message isthe same as any of the first primary cell and secondary cells in thefirst group of secondary cells while the index of the second primarycell is not same as index of any one of the secondary cells in the firstgroup of secondary cells; updating the second primary cell indexaccording to the received message; initiating random access to thesecond primary cell; continuing data transmission and or reception onthe one or more secondary cells of the first group of secondary cellswhose index (indices) is the same as any one of the second primary cellor secondary cell of the second group of secondary cells between theterminal device and the network device.

In one embodiment, the method further comprises: in response to it beingdetected that index of the second primary cell is same as any one of thesecondary cells in the first group of secondary cells; updating thesecond primary cell index according to the received message; continuingdata transmission and or reception on the one or more secondary cells ofthe first group of secondary cells whose index(indices) are the same asany one secondary cell of the second group of secondary cells betweenthe terminal device and the network device.

In a fourth aspect of the disclosure, there is provided a terminaldevice. The terminal device includes: a receiving unit 710 configured toreceive a message transmitted from a network device, the message beingconfigured by detecting whether layer 2 context being kept and/or one ormore serving secondary cells remain for a primary cell change for theterminal device; an obtaining unit 720 configured to obtain informationof the primary cell change from the received message; a performing unit730 configured to perform the primary cell change based on theinformation.

In a fifth aspect of the disclosure, there is provided a network device.The network device includes: a processor and a storage medium, thestorage medium containing instructions that, when executed on theprocessor, cause the network device to: detect whether layer 2 contextbeing kept and/or one or more serving secondary cells remain for aprimary cell change for a terminal device; configure a messageindicating a primary cell change based on the detecting; transmit themessage to the terminal device.

In a sixth aspect of the disclosure, there is provided a terminaldevice. The terminal device includes: a processor and a storage medium,the storage medium containing instructions that, when executed on theprocessor, cause the terminal device to: receive a message transmittedfrom a network device, the message being configured by detecting whetherlayer 2 context being kept and/or one or more serving secondary cellsremain for a primary cell change for the terminal device; obtaininformation of the primary cell change from the received message;perform the primary cell change based on the information.

In a seventh aspect of the disclosure, there is provided a computerprogram. The instructions which, when executed on at least oneprocessor, cause the at least one processor to carry out the methodaccording to the first aspect of the disclosure.

In an eighth aspect of the disclosure, there is provided a computerprogram. The instructions which, when executed on at least oneprocessor, cause the at least one processor to carry out the methodaccording to the third aspect of the disclosure.

According to the various aspects and embodiments as mentioned above, thetime period for the change of primary cell could be reduced and thus thedelayed or interrupted data transmission during the primary cell changecould be optimized.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and benefits of variousembodiments of the disclosure will become more fully apparent, by way ofexample, from the following detailed description with reference to theaccompanying drawings, in which like reference numerals or letters areused to designate like or equivalent elements. The drawings areillustrated for facilitating better understanding of the embodiments ofthe disclosure and not necessarily drawn to scale, in which:

FIG. 1 shows an environment of a wireless communication network 100 inwhich embodiments of the present disclosure may be implemented;

FIG. 2 shows a flowchart of a method 200 at a network device inaccordance with an embodiment of the present disclosure;

FIG. 3 shows a flowchart of a method 300 at a network device inaccordance with an embodiment of the present disclosure;

FIG. 4 shows a flowchart of a method 400 at a terminal device inaccordance with an embodiment of the present disclosure;

FIG. 5 shows a flowchart of a method 500 at a terminal device inaccordance with an embodiment of the present disclosure;

FIG. 6 shows a block diagram of a network device 600 in accordance withan embodiment of the present disclosure;

FIG. 7 shows a block diagram of a terminal device 700 in accordance withan embodiment of the present disclosure; and

FIG. 8 shows a simplified block diagram 800 of a device that is suitablefor use in implementing embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure will now be discussed with reference to severalexample embodiments. It should be understood that these embodiments arediscussed only for the purpose of enabling those skilled persons in theart to better understand and thus implement the present disclosure,rather than suggesting any limitations on the scope of the presentdisclosure.

As used herein, the term “wireless communication network” refers to anetwork following any suitable communication standards, such asLTE-Advanced (LTE-A), LTE, Wideband Code Division Multiple Access(WCDMA), High-Speed Packet Access (HSPA), and so on. Furthermore, thecommunications between a terminal device and a network device in thewireless communication network may be performed according to anysuitable generation communication protocols, including, but not limitedto, the first generation (1G), the second generation (2G), 2.5G, 2.75G,the third generation (3G), the fourth generation (4G), 4.5G, the futurefifth generation (5G) communication protocols, and/or any otherprotocols either currently known or to be developed in the future.

The term “network device” refers to a device in a wireless communicationnetwork via which a terminal device accesses the network and receivesservices therefrom. The network device refers a base station (BS), anaccess point (AP), a Mobile Management Entity (MME),Multi-cell/Multicast Coordination Entity (MCE), a gateway, a server, acontroller or any other suitable device in the wireless communicationnetwork. The BS may be, for example, a node B (NodeB or NB), an evolvedNodeB (eNodeB or eNB), a Remote Radio Unit (RRU), a radio header (RH), aremote radio head (RRH), a relay, a low power node such as a femto, apico, and so forth.

The term “terminal device” refers to any end device that can access awireless communication network and receive services therefrom. By way ofexample and not limitation, the terminal device refers to a mobileterminal, UE, or other suitable device. The UE may be, for example, aSubscriber Station (SS), a Portable Subscriber Station, a Mobile Station(MS), or an Access Terminal (AT). The terminal device may include, butnot limited to, portable computers, image capture terminal devices suchas digital cameras, gaming terminal devices, music storage and playbackappliances, a mobile phone, a cellular phone, a smart phone, a tablet, awearable device, a personal digital assistant (PDA), a vehicle, apedestrian and the like.

As used herein, the terms “first” and “second” refer to differentelements. The singular forms “a” and “an” are intended to include theplural forms as well, unless the context clearly indicates otherwise.The terms “comprises,” “comprising,” “has,” “having,” “includes” and/or“including” as used herein, specify the presence of stated features,elements, and/or components and the like, but do not preclude thepresence or addition of one or more other features, elements, componentsand/or combinations thereof. The term “based on” is to be read as “basedat least in part on.” The term “one embodiment” and “an embodiment” areto be read as “at least one embodiment.” The term “another embodiment”is to be read as “at least one other embodiment.” Other definitions,explicit and implicit, may be included below.

Now some exemplary embodiments of the present disclosure will bedescribed below with reference to the figures. Reference is first madeto FIG. 1, which illustrates an environment of a wireless communicationnetwork 100 in which embodiments of the present disclosure may beimplemented. As shown in FIG. 1, the wireless communication network 100includes a network device with carrier aggregation, which is implementedas a BS 110, and a terminal device 120. The BS 110 acts as a servingnode of the terminal device 120. In particular, the BS 110 provides twocomponent carriers 170 and 180, and the terminal device 120 is served bythe

BS 110 via the component carriers 170 and 180. Correspondingly, thereare a number of serving cells for example 130 and 140, one for eachcomponent carrier such as the component carrier 170 and 180. Theterminal device 120 is configured for carrier aggregation and receivesfrom BS 110 the component carrier 170 and the component carrier 180wherein 130 is a primary cell (Pcell) while 140 is a secondary cell(Scell). The concepts of component carrier and cell may beinterchangeable in the discussion of the disclosure.

The wireless communication network 100 may follow any suitablecommunication standards, such as LTE-Advanced (LTE-A), LTE, WidebandCode Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA),and so on. Furthermore, the communications between the terminal device120 and the BS 110/111 in the network 100 may be performed according toany suitable generation communication protocols, including, but notlimited to, the first generation (1G), the second generation (2G), 2.5G,2.75G, the third generation (3G), the fourth generation (4G), 4.5G, thefuture fifth generation (5G) communication protocols, and/or any otherprotocols either currently known or to be developed in the future.

To facilitate the discussions of the disclosure, the current primarycell 130 could be referred to as the first primary cell which means theprimary cell serving the terminal device 120 before the primary cellchange completes. The new primary component cell could be referred to asthe target primary cell or the second primary cell 150 which means theprimary cell to serve the terminal device 120 after the primary cellchange completes. The first primary cell 130 serves the terminal device120 together with a first group of secondary cells 140. Correspondingly,the second primary cell 150 is to serve the terminal device 120 togetherwith a second group of secondary cells 160. The first group or thesecond group of secondary cells may include one or more secondary cells,the number of the secondary cells of the first group or the second groupsubject to the configuration of the carrier aggregation.

Conventionally, when the terminal device 120 finds that the quality ofcurrent primary component cell 130 is not good enough due to variousreasons, for example the primary cell radio quality is deteriorating, orthe radio quality of other cell or carrier is becoming better bymeasuring all the neighboring cell or carriers, the terminal device 120sends a report to the BS 110. Upon receipt of the report from theterminal device 120, the terminal device 110 determines a target orsecond primary cell 150 for the terminal device 120 as well as a secondgroup of secondary cells 160. In embodiments of the present disclosure,the determining of the second primary cell 150 and/or the second groupof secondary cells 160 may be implemented in a variety of ways, which isconventional and thus is not detailed herein. The second primary cell150 can be provided by another BS 111 as shown in FIG. 1 or provided byBS 110 which provides the first primary cell 130 as well.

Conventionally, the BS 110 sends a message indicating a primary cellchange to the terminal device 120 and instructing the terminal device120 to perform the primary cell change. During the process, a handoverprocedure is needed which means RRCConnectionReconfiguration messageincluding MobiltyControlInfo is sent to the terminal device 120, whichwill then trigger PDCP/RLC reestablishment, MAC reset, new keyderivation, and perform the random access procedure to the secondaryprimary cell 150. Usually this procedure will take relatively long timeperiod for example 40 ms, and during this period, data transmission isdelayed or interrupted.

In order to solve the above and other potential problems, embodiments ofthe present disclosure provides an efficient way to perform a primarycell change. In accordance with embodiments of the present disclosure,upon receipt of measurement report on quality of all neighboring celland carriers including one or more of the first primary cell 140 andsecond primary cell 150 from the terminal device 120, the BS 110determines a second primary cell 150 and a second group of secondarycells 160 and detects whether layer 2 context being kept and/or one ormore serving secondary cells remain for a primary cell change for theterminal device 120 and configures a message indicating the primary cellchange based on the detecting and then transmit the message to theterminal device 120. When entire of layer 2 context being kept, the BS110 configures the message by including at least a security informationelement to require the terminal device 120 to derive a new security keyand transmits the message to the terminal device 120. When part of thelayer 2 context for example PDCP entity being kept, the BS 110configures the message by including at least an information element totrigger reconfiguring of RLC/MAC entity and transmits the message to theterminal device 120. When entire of layer 2 context being kept and theindex of the second primary cell 150 is not same as any secondary cellof the first group of secondary cells 140, the BS 110 configures themessage by including at least ID information of the second group ofsecondary cells 160 and transmits the message to the terminal device120. When the index of the second primary cell is same as one secondarycell of the first group of secondary cells, the BS 110 configures themessage by including at least ID information of the second primary cell150 and transmits the message to the terminal device 120.

In this way, by detecting the relationship between the first set ofcells including the first primary cell 130 and the first group ofsecondary cells 140 and the second set of cells including the secondprimary cell 150 and the second group of secondary cells 160 andconfiguring the message of primary cell change accordingly, differentmeans to perform the primary cell change may be performed among whichprimary cell change may complete without the handover procedure in somescenarios. As a result, it is possible to reduce the time period andoptimize the data transmission during the period of primary cell change.

It is to be understood that the configuration of FIG. 1 is describedmerely for the purpose of illustration, without suggesting anylimitation as to the scope of the present disclosure. Those skilled inthe art will appreciate that the wireless communication network 100 mayinclude any suitable number of terminal device and BS s and may haveother suitable configurations, and each BS may provide any suitablenumber of carriers or cells.

Now reference is made to FIG. 2, which shows a flowchart of a method 200for primary cell change implemented at a device in accordance with anembodiment of the present disclosure. With the method 200, the above andother potential deficiencies in the conventional approaches can beovercome. It would be appreciated by those skilled in the art that themethod 200 may be implemented at a network device, such as the BS 110 orother suitable devices. For the purpose of illustration, the method 200will be described below with reference to the BS 110 in the wirelesscommunication system 100.

The method 200 is entered in block 201, where whether layer 2 contextbeing kept and/or one or more serving secondary cells remain for aprimary cell change for a terminal device is detected.

In embodiments of the present disclosure, the network device 110 detectswhether layer 2 context being kept for a primary cell change for aterminal device 120. The layer 2 context refers to the entities,parameters or other information about the layer 2 for example the MACHARQ state, RLC Tx/Rx status, which packets are received or not, PDCPTX/RX status, packet header compression state, and QoS state, UEpriority and etc. Layer 2 context is common to a set of cells includinga primary cell and a group of secondary cells which together serve theterminal device 120. Layer 2 context corresponding to the first primarycell 130 or the second primary cell 150 refer to the layer 2 contextcommon to a set of cells serving the terminal device 120 including thefirst primary cell 130 and the first group of secondary cells 140 or thesecond primary cell 150 and the second group of secondary cells 160.When the layer 2 context corresponding to the first primary cell 130 andthe first group of secondary cells 140 is different from the layer 2context corresponding to the second primary cell 150 and the secondgroup of secondary cells 160 depends on the eNB logical architecture. Inone embodiment, all protocol entities are implemented in one logicalnode, then the entire L2 context may change when the logical nodechanges. In another embodiment, PDCP can be implemented in one logicalnode, while RLC/MAC can be implemented in another logical node, and thenonly part of the L2 context can be changed. Layer 2 context being keptmay include part or entire of the layer 2 context keep the same. Layer 2context being kept for a primary cell change for a terminal device mayinclude part or entire of the layer 2 context corresponding to a firstset of first primary cell 130 and the first group of secondary cell 140keeps the same or not comparing to the one corresponding to the secondset of cells of the second primary cell 150 and the second group ofsecondary cell 160. That is to say, to detect whether layer 2 contextchanges or not after the primary cell change. In still anotherembodiment, part of layer 2 context being kept may include the contextfor MAC and RLC changes while the context for PDCP for example PDCPentity remains the same or unchanged which may happen when the eNBarchitecture is split into different logical nodes where PDCP is withinone logical node while RLC/MAC is within another logical node and thusit is possible that the entity of RLC/MAC may change while PDCP entitydoes not change.

In embodiments of the present disclosure, that the network device 110detects whether one or more serving secondary cells remain for a primarycell change for a terminal device may include at least one secondarycells of the first set of cells remain the same as any cells of thesecond set of cells. That is to say, one or more of the secondary cellsserving the terminal device 120 remain in the second set of cells toserve the terminal device 120. Observing from the terminal device side,the secondary cell(s) is serving and continues to serve the terminaldevice 120 before and after the primary cell change. The network device110 detects whether one or more serving secondary cells remain for aprimary cell change for a terminal device in a variety of ways. In anembodiment, the network device 110 detects whether the index (indices)of any secondary cells of the first set of cells is the same of anycells of the second set of cells. The serving secondary cell(s) 140 toremain in the second set of cells could be secondary cell(s) 160 or actas the second primary cell 150 after the primary cell change completes.

In embodiments of the present disclosure, the network device 110 detectslayer 2 context being kept and one or more serving secondary cellsremain for a primary cell change for the terminal device 120. Thenetwork device 110 may first detects whether layer 2 context being keptfor a primary cell change for the terminal device 120 and then detectswhether one or more serving secondary cells remain for a primary cellchange for the terminal device 120. Optionally, the network device 110may first detects whether one or more serving secondary cells remain fora primary cell change for the terminal device 120 and then detectswhether layer 2 context being kept for a primary cell change for theterminal device 120.

In block 220, the network device 110 configures a message of primarycell change based on the detecting. In some embodiments, when it isdetected that entire of layer 2 context not being kept or all of thelayer 2 context changes, the network device 110 configure the message byincluding at least a security information element to require theterminal device 120 to derive a new security key, in this scenario, theother information or parameters necessary for performing primary cellchange is also included in the message, for example, the ID informationof the second primary cell 150 and the second group of secondary cells160, the configuration for the second primary cell 150, the new physicallayer parameter setting, the new MAC/RLC/PDCP setting, the new DRBsetting etc. When it is detected that entire of layer 2 context exceptPDCP entity corresponding to the second primary cell 150 not being keptcomparing to the first primary cell 130, the network device 110configures the message by including at least an information element totrigger reconfiguring of RLC/MAC entity, that is to say, when it'sdetected that only PDCP entity does not change while all the other layer2 context changes such as the MAC or RLC, the network device 110configures the message by including at least an information element totrigger reconfiguring of RLC/MAC entity, the security informationelement to require the terminal device 120 to derive a new security keyis thus not included in the message, in this scenario, the otherinformation or parameters necessary for performing primary cell changeis also included in the message, for example, the ID information of thesecondary primary cell 150 and the second group of secondary cells 160,the configuration for the second primary cell 150, the new physicallayer parameter setting, the new MAC/RLC setting and etc. When it isdetected that entire of layer 2 context being kept and the index of thesecond primary cell is not same as any secondary cell of the first groupof secondary cells 140, the network device 110 configures the message byincluding at least ID information of the second primary cell 150 andsecond group of secondary cells 160, in this scenario, the otherinformation or parameters necessary for performing primary cell changeis also included in the message, for example, new physical layerparameter setting and the configuration for the second primary cell 150.When it is detected that the index of the second primary cell 130 issame as one secondary cell of the first group of secondary cells 140,the terminal device 110 configure the message by including at least IDinformation of the second primary cell 150, in this scenario, the otherinformation or parameters necessary for performing primary cell changeis also included in the message, such as the ID information of thesecond group of secondary cells 160, in this scenario, the configurationfor the second primary cell 150 may not be included in the message. Insome of the embodiments illustrated above, based on the configuredmessage, the process of handover procedure is not needed and thus mayreduce the time period and optimize the data transmission during theprocess of primary cell change.

In some embodiments, the message can be a MAC message or Radio ResourceControl (RRC) message such as an RRC Connection Reconfiguration message,or any other suitable message. The MAC message may include a MAC controlelement which is identified by a Logical Channel ID. Alternatively, theMAC message may include a MAC control element which indicates index ofthe second primary cell 150. In an embodiment, when it is detected thatthe index of the second primary cell is same as one secondary cell ofthe first group of secondary cells, the message may be configured via aMAC message and RRC procedure may be used for the other scenarios. Forthe scenario using the MAC message, a new MAC CE (control element) isdefined which is used to notify the terminal device 120 the index of thesecond primary cell 150. The new MAC CE is identified by a LogicalChannel ID.

In block 230, the network device 110 transmits the configured message tothe terminal device 120 indicating the primary cell change andinstructing the terminal device 120 to perform the primary cell change.In some embodiments, the message is transmitted via all existingcomponent cells controlled by the network device 110 which continuestransmitting the MAC control element until receiving a HARQ ACK from oneof the component cells corresponding to this MAC control elementtransmission.

Now some example embodiments will be described with respect to FIG. 3.FIG. 3 shows a flowchart of a method 300 for primary cell changeimplemented at a network device in accordance with an embodiment of thepresent disclosure. The method 300 may be considered as a specificimplementation of the method 200 described above with reference to FIG.3. However, it is noted that this is only for the purpose ofillustrating the principles of the present disclosure, rather thanlimiting the scope thereof.

The method 300 is entered in block 310, where the BS 110 determines thesecond primary cell 150 for the terminal device 120.

In block 320, the network device 110 detects whether entire of layer 2context being kept for the primary cell change, when it's detected thatthe entire of layer 2 context not being kept, the network device 110configures the message by including at least a security informationelement to require the terminal device 120 to derive a new security key.When it's detected that the not entire or all of layer 2 context changesfor the primary cell change, the method 300 proceeds to block 340, wherethe network device 110 detects whether PDCP entity keeps the same forthe primary cell change, when it's detected that PDCP entity keep thesame for the primary cell change but MAC/RLC entity changes, the networkdevice 110 configures the message by including at least an informationelement to trigger reconfiguring of RLC/MAC entity. When it's detectedthat entire layer 2 context keeps the same for the primary cell change,the method 300 proceeds to block 360, where the network device 110detects whether the index of the second primary cell 150 is same as onesecondary cell of the first group of secondary cells 140. When it'sdetected that the index of the second primary cell 150 is not same asone secondary cell of the first group of secondary cells 140, thenetwork device 110 configures the message by including at least IDinformation of the second group of secondary cells 160. When it'sdetected that the index of the second primary cell 150 is same as onesecondary cell of the first group of secondary cells 140, the networkdevice 110 configures the message by including at least ID informationof the second primary cell 150.

In this way, various scenarios based on the detected relationshipbetween the first set of cells and the second set of cells can betreated differently. This helps to reduce the time period of performingthe primary cell change and optimize the data transmission during theprocess.

FIG. 4 shows a flowchart of a method 400 for primary cell changeimplemented at a terminal device in accordance with an embodiment of thepresent disclosure. With the method 400, the above and other potentialdeficiencies in the conventional approaches can be overcome. It would beappreciated that the method 400 may be implemented by a device, such asthe terminal device 120 or other suitable devices. For the purpose ofillustration, the method 400 will be described below with reference tothe terminal device 120 in the wireless communication system 100.

The method 400 is entered in block 410, where a message of primary cellchange is received from a network device. The message is configured bythe network device, for example, the BS 110, based on detecting thefirst set of cells and the second set of cells. The configuration of themessage may be implemented according to the method 200 or the method 300as discussed above, and thus the details are not repeated here.

In block 420, where the terminal device 120 detects the information ofprimary cell change from the received message transmitted from thenetwork device 110. In some embodiments of present disclosure, themessage may include an information element for derivation of a newsecurity key, an information element to trigger reconfiguring ofRLC/MAC, ID information of the second group of secondary cells, IDinformation of the second primary cell, configuration for the secondprimary cell, the new physical layer parameter setting, the newMAC/RLC/PDCP setting, the new DRB setting and other informationnecessary for the primary cell change.

In block 430, when it is detected that the received message includes aninformation element for derivation of a new security key, the terminaldevice 120 derives a new security key, updates the second primary cellindex according to the received message, resets MAC; re-establishesPDCP/RLC; and initiates random access to the second primary cell to getsync with the second primary cell 150. In this scenario, a standardhandover procedure is followed and the details are omitted herein forsimplicity of the discussion. The security key corresponds to a layer 2context, when entire of the layer 2 context changes, the security keymay change and a new security key may be needed, when part or entire ofthe layer 2 context keeps the same, the security key may keep the same,for example, if PDCP does not change while MAC and RLC change, there isno need to generate a new security key at the terminal device 120 toperform the primary cell change.

When it is detected that the received message includes an informationelement to trigger reconfiguring of RLC/MAC, but no information elementfor derivation of a new security key, the terminal device 120 updatesthe second primary cell index according to the received message; resetsMAC; re-establishes RLC; and initiates random access to get sync withthe second primary cell 150. In this scenario, there is no need toderive a new security key, thus the time period to perform the primarycell change may be reduced.

When it is detected that the received message does not include aninformation element for derivation of a new security key or aninformation element for triggering reconfiguring of RLC/MAC while theindex of any of the second set of cells including second primary cell150 and secondary cells in the second group of secondary cells 160included in the message is not the same as the index of first set ofcells including the first primary cell 130 and secondary cells in thefirst group of secondary cells 140, the terminal device 120 updates thesecond primary cell index according to the received message andinitiates random access to the second primary cell 150. In anembodiment, the terminal device 120 first detects whether the receivedmessage includes an information element for derivation of a new securitykey, if no, then detects whether the received message includes aninformation element for triggering reconfiguring of RLC/MAC, if no, thendetects whether the index of any of the second primary cell 150 andsecondary cells in the second group of secondary cells 160 included inthe message is the same as the first primary cell 130 and secondarycells in the first group of secondary cells 140; in another embodiment,the terminal device 120 first detects whether the received messageincludes an information element for triggering reconfiguring of RLC/MAC,if no, then detects whether the received message includes an informationelement for derivation of a new security key, if no, then detectswhether the index of any of the second primary cell 150 and secondarycells in the second group of secondary cells 160 included in the messageis the same as the first primary cell 130 and secondary cells in thefirst group of secondary cells 140; in another embodiment, the terminaldevice 120 first detects whether the index of any of the second primarycell 150 and secondary cells in the second group of secondary cells 160included in the message is the same as the first primary cell 130 andsecondary cells in the first group of secondary cells 140, if no, thendetects whether the received message includes an information element forderivation of a new security key, if no, then detects whether thereceived message includes an information element for triggeringreconfiguring of RLC/MAC; in still another embodiment, the terminaldevice 120 first detects whether the index of any of the second primarycell 150 and secondary cells in the second group of secondary cells 160included in the message is the same as the first primary cell 130 andsecondary cells in the first group of secondary cells 140, if no, thendetects whether the received message includes an information element fortriggering reconfiguring of RLC/MAC; then detects whether the receivedmessage includes an information element for derivation of a new securitykey. In this scenario, there is no need to reset MAC, re-establish RLCor derive a new security key at the terminal device 120, thus the timeperiod to perform the primary cell change may be reduced substantially.

When it is detected that the index (indices) of one or more of thesecond primary cell 150 and secondary cells in the second group ofsecondary cells 160 included in the message is the same as the firstprimary cell 130 and secondary cells in the first group of secondarycells 140 while the index of the second primary cell 150 is not same asindex of any one of the secondary cells in the first group of secondarycells 140, the terminal device 120 updates the second primary cell indexaccording to the received message, initiates random access to get syncwith the second primary cell 150, while the data transmission and orreception on the one or more secondary cells of the first group ofsecondary cells 140 whose index (indices) is the same as any onesecondary cell of the second group of secondary cells 160 between theterminal device 120 and the network device 110 continues during theprimary cell change. In this scenario, there is no need to reset MAC,re-establish RLC and derive a new security key at the terminal device120 during the primary cell change, and meanwhile, since one or more ofthe secondary cells remain or maintain before and after the primary cellchange, hence, the data transmission and or reception between theterminal device 120 and the network device 110 can be maintained via theone or more of the secondary cells, thus the time period to perform theprimary cell change may be reduced and the data transmission and orreception between the terminal device 120 and the network device 110would not be delayed or interrupted and the user experience could beimproved considerably.

When it is detected that the index of the second primary cell 150 issame as index of any one of the secondary cells in the first group ofsecondary cells 140, the terminal device 120 updates the second primarycell index according to the received message, and the data transmissionand or reception on the one or more secondary cells of the first groupof secondary cells 140 whose index is the same as any one of thesecondary primary cell 150 and secondary cell of the second group ofsecondary cells 160 between the terminal device 120 and the networkdevice 110 can be maintained. In this scenario, there is no need toreset MAC, re-establish RLC, derive a new security key, initiate randomaccess to get sync with the second primary cell 150 at the terminaldevice 120 during the primary cell change, and meanwhile, since one ormore of the secondary cells remain or maintain before and after theprimary cell change, hence, the data transmission and or receptionbetween the terminal device 120 and the network device 110 can bemaintained via the one or more of the secondary cells, thus the timeperiod to perform the primary cell change may be reduced considerablyand the data transmission and or reception between the terminal deviceand the network device would not be interrupted and the user experiencecould be improved greatly.

Now some example embodiments will be described with respect to FIG. 5.FIG. 5 shows a flowchart of a method 500 for primary cell changeimplemented at a terminal device in accordance with an embodiment of thepresent disclosure. The method 500 may be considered as a specificimplementation of the method 400 described above with reference to FIG.4. However, it is noted that this is only for the purpose ofillustrating the principles of the present disclosure, rather thanlimiting the scope thereof.

The method 500 is entered in block 510, where the terminal device 120receives a message transmitted from the network device 110. The messageincludes information indicating a primary cell change.

In block 520, the terminal device 120 detects whether the receivedmessage includes an information element for derivation of a new securitykey, when it's detected that the received message includes aninformation element for derivation of a new security key, the terminaldevice 120 performs a standard handover procedure for the primary cellchange. When it's detected that the received message does not include aninformation element for derivation of a new security key, the method 500proceeds to block 540, where the terminal device 120 detects whether thereceived message include the information element to triggerreconfiguring of RLC/MAC, when it's detected that the received messageincludes an information element to trigger reconfiguring of RLC/MAC, theterminal device 120 updates the second primary cell index according tothe received message, resets MAC, re-establishes RLC and initiatesrandom access to get synch with the second primary cell 150. When it'sdetected that the received message does not include an informationelement to trigger reconfiguring of RLC/MAC, the method 500 proceeds toblock 560, where the terminal device 120 detects whether index (indices)of any of the second primary cell 150 and secondary cells in the secondgroup of secondary cells 160 included in the message is the same as thefirst primary cell 130 and secondary cells in the first group ofsecondary cells 140. When it's detected that index (indices) of any ofthe second primary cell 150 and secondary cells in the second group ofsecondary cells 160 included in the message is not the same as the firstprimary cell 130 and secondary cells in the first group of secondarycells 140, the terminal device 120 updates the second primary cell indexaccording to the received message and initiates random access to getsync with the second primary cell 150. When it's detected that index(indices) of any of the second primary cell 150 and secondary cells inthe second group of secondary cells 160 included in the message is thesame as the first primary cell 130 and secondary cells in the firstgroup of secondary cells 140, the method 500 proceeds to block 580,where the terminal device 120 detects whether index of the secondprimary cell 150 is same as any one of the secondary cells in the firstgroup of secondary cells 140. When it's detected that index of thesecond primary cell 150 is not same as any one of the secondary cells inthe first group of secondary cells 140, the terminal device 120 updatesthe second primary cell index according to the received message,initiates random access to get sync with the second primary cell 150 andthe data transmission and or reception on the one or more secondarycells of the first group of secondary cells 140 whose index is the sameas any one secondary cell of the second group of secondary cells 160between the terminal device 120 and the network device 110 continues.When it's detected that index of the second primary cell 150 is same asany one of the secondary cells in the first group of secondary cells140, the terminal device 120 updates the second primary cell indexaccording to the received message and the data transmission and orreception on the one or more secondary cells of the first group ofsecondary cells 140 whose index is the same as any one of the secondprimary cell 150 and secondary cell of the second group of secondarycells 160 between the terminal device 120 and the network device 110continues.

In this way, various scenarios based on the detected relationshipbetween the first set of cells and the second cells can be treateddifferently. This helps to reduce the time period of performing theprimary cell change and optimize the data transmission during theprocess.

Now reference is made to FIG. 6 shows a block diagram of a device 600 inaccordance with an embodiment of the present disclosure. It would beappreciated that the device 600 may be implemented at a network device,such as the BS 110 as shown in FIG. 1, a server, a controller or othersuitable devices.

As shown, the network device 600 includes a detecting unit 610, aconfiguration unit 620 and a transmitting unit 630. The detecting unit610 is configured to detect whether layer 2 context being kept and/orone or more serving secondary cells remain for a primary cell change fora terminal device, the configuration unit 620 is configured to configurea message indicating a primary cell change based on the detecting by thedetecting unit 610, the transmitting unit 630 is configured to transmitthe message to the terminal device 120.

In an embodiment, the configuration unit 620 is further configured to,in response to it being detected that entire of the layer 2 context notbeing kept, configure the message by including at least an informationelement to require the terminal device 120 to derive a new security key.

In an embodiment, the configuration unit 620 is further configured to,in response to it being detected that entire of the layer 2 contextexcept PDCP entity corresponding to the second primary cell 150 notbeing kept comparing to the first primary cell 130, configure themessage by including at least an information element to triggerreconfiguring of RLC/MAC entity.

In an embodiment, the configuration unit 620 is further configured to,in response to it being detected that entire of layer 2 context beingkept while the index of the second primary cell 150 is not same as anysecondary cell of the first group of secondary cells 140, configure themessage by including at least ID information of the second group ofsecondary cells 160.

In an embodiment, the configuration unit 620 is further configured to,in response to it being detected that the index of the second primarycell 150 is same as one secondary cell of the first group of secondarycells 140, configure the message by including at least ID information ofthe second primary cell 150.

Now reference is made to FIG. 7 which shows a block diagram of anapparatus 700 implemented at a terminal device in accordance with anembodiment of the present disclosure. It would be appreciated that theapparatus 700 may be implemented at a terminal device or other suitabledevices.

As shown, the apparatus 700 includes a receiving unit 710, an obtainingunit 720, and a performing unit 730. The receiving unit 710 isconfigured to receive a message transmitted from a network device, themessage being configured by detecting whether layer 2 context being keptand/or one or more serving secondary cells remain for a primary cellchange for the terminal device 120, the obtaining unit 720 is configuredto obtain information of the primary cell change from the receivedmessage, the performing unit 730 is configured to perform the primarycell change based on the information.

In an embodiment, the terminal device 120 may further include a judgingunit 740, the judging unit 740 is configured to judge whether thereceived message includes an information element for derivation of a newsecurity key; or judge whether the received message includes aninformation element to trigger reconfiguring of RLC/MAC; or judgewhether the index (indices) of any one of the second primary cell 150and the second group of secondary cells 160 included in the message isthe same as the first primary cell 130 and the first of group secondarycells 140; or judge whether the index of the second primary cell 150included in the message is same as index of any one of the first groupof secondary cells 140.

In an embodiment, the performing unit 730 is further configured to, inresponse to it being detected that the received message includes theinformation element for derivation of a new security key, derive asecond security key, reset MAC, re-establish PDCP/RLC and initiaterandom access to get sync with the second primary cell 150.

In an embodiment, the performing unit 730 is further configured to, inresponse to it being detected that the received message includes aninformation element to trigger reconfiguring of RLC/MAC but not aninformation element for derivation of a new security key, update thesecond primary cell index according to the received message, reset MAC,re-establish RLC and initiate random access to get sync with the secondprimary cell 150.

In an embodiment, the performing unit 730 is further configured to, inresponse to the received message does not include an information elementfor derivation of a new security key or trigger reconfiguring of RLC/MACwhile the index (indices) of any of the second primary cell 150 and thesecond group of secondary cells 160 included in the message is not thesame as the first primary cell 130 and the first group of secondarycells 140, update the second primary cell index according to thereceived message and initiate random access to get sync with the secondprimary cell 150.

In an embodiment, the performing unit 730 is further configured to, inresponse to it being detected that the received message does not includean information element for derivation of a new security key or triggerreconfiguring of RLC/MAC while the index (indices) of one or more of thesecond primary cell 150 and secondary cells in the second group ofsecondary cells 160 included in the message is the same as the firstprimary cell 130 and secondary cells in the first group of secondarycells 140 while the index of the second primary cell 150 is not same asindex of any one of the secondary cells in the first group of secondarycells 140, update the second primary cell index according to thereceived message, initiate random access to get sync with the secondprimary cell 150 and continue data transmission and or reception on theone or more secondary cells of the first group of secondary cells 140whose index (indices) is the same as any one secondary cell of thesecond group of secondary cells 160 between the terminal device 120 andthe network device 110.

In an embodiment, the performing unit 730 is further configured to, inresponse to it being detected that the received message does not includean information element for derivation of a new security key or triggerreconfiguring of RLC/MAC while the index of the second primary cell 150is same as index of any one of the first group of secondary cells 140,update the second primary cell index according to the received messageand continue data transmission and or reception on the one or moresecondary cells of the first group of secondary cells 140 whose index(indices) is the same as any one of the first primary cell 150 andsecondary cell of the second group of secondary cells 160 between theterminal device 120 and the network device 110.

It should be appreciated that components included in the apparatus 600correspond to the operations of the methods 200 and 300, and componentsincluded in the apparatus 700 correspond to the operations of themethods 400 and 500. Therefore, all operations and features describedabove with reference to FIGS. 2 and 3 are likewise applicable to thecomponents included in the apparatus 600 and have similar effects, andall operations and features described above with reference to FIGS. 4and 5 are likewise applicable to the components included in theapparatus 700 and have similar effects. For the purpose ofsimplification, the details will be omitted.

The components included in the apparatuses 600 and 700 may beimplemented in various manners, including software, hardware, firmware,or any combination thereof. In one embodiment, one or more units may beimplemented using software and/or firmware, for example,machine-executable instructions stored on the storage medium. Inaddition to or instead of machine-executable instructions, parts or allof the components included in the apparatuses 600 and 700 may beimplemented, at least in part, by one or more hardware logic components.For example, and without limitation, illustrative types of hardwarelogic components that can be used include Field-programmable Gate Arrays(FPGAs), Application-specific Integrated Circuits (ASICs),Application-specific Standard Products (ASSPs), System-on-a-chip systems(SOCs), Complex Programmable Logic Devices (CPLDs), and the like.

In accordance with embodiments of the present disclosure, there isprovided an apparatus implemented at a network device. The apparatusincludes: means for detecting whether layer 2 context being kept and/orone or more serving secondary cells remain for a primary cell change fora terminal device; means for configuring a message indicating a primarycell change based on the detecting; and means for transmitting themessage to the terminal device.

In an embodiment, the means for configuring a message indicating aprimary cell change based on the detecting may include: means for, inresponse to it being detected that entire of the layer 2 context notbeing kept, configuring the message by including at least securityinformation element to require the terminal device to derive a newsecurity key.

In an embodiment, the means for configuring a message indicating achange of primary cell based on the detecting may include: means for, inresponse to it being detected that entire of the layer 2 context exceptPDCP entity corresponding to the second primary cell not being keptcomparing to the first primary cell, configuring the message byincluding at least information element to trigger reconfiguring ofRLC/MAC entity.

In an embodiment, the means for configuring a message indicating aprimary cell change based on the detecting may include: means for, inresponse to it being detected that entire of layer 2 context being keptwhile the index of the second primary cell is not same as any secondarycell of the first group of secondary cells, configuring the message byincluding at least ID information of the second group of secondarycells.

In an embodiment, the means for configuring a message indicating aprimary cell change based on the detecting may include: means for, inresponse to it being detected that the index of the second primary cellis same as one secondary cell of the first group of secondary cells,configuring the message to include at least ID information of the secondprimary cell.

In accordance with embodiments of the present disclosure, there isprovided an apparatus implemented at a terminal device. The apparatusincludes: means for receiving a message transmitted from a networkdevice, the message being configured by detecting whether layer 2context being kept and/or one or more serving secondary cells remain fora primary cell change for the terminal device, means for obtaininginformation of the primary cell change from the received message; andmeans for performing the primary cell change based on the information.

In an embodiment, the terminal device further includes means for judgingwhether the received message includes an information element forderivation of a new security key; or judging whether the receivedmessage includes an information element to trigger reconfiguring ofRLC/MAC; or judging whether the index (indices) of any of the secondprimary cell and the second group secondary cells included in themessage is not the same as the first primary cell and the second groupsecondary cells; or judging whether the index of the second primary cellincluded in the message is same as index of any one of the first groupof secondary cells.

In an embodiment, the means for performing the primary cell change basedon the information includes means for, in response to it being detectedthat the received message includes the information element forderivation of a new security key, deriving a second security key,resetting MAC, re-establishing PDCP/RLC and initiating random access tothe second primary cell.

In an embodiment, the means for performing the primary cell change basedon the information includes means for, in response to it being detectedthat the received message includes an information element to triggerreconfiguring of RLC/MAC, updating the second primary cell indexaccording to the received message, resetting MAC, re-establishing RLCand initiating random access to the second primary cell.

In an embodiment, the means for performing the primary cell change basedon the information includes means for, in response to the receivedmessage does not include an information element for derivation of a newsecurity key or trigger reconfiguring of RLC/MAC while the index(indices) of any of the second primary cell and the second groupsecondary cells included in the message is not the same as the firstprimary cell and the second group secondary cells, updating the secondprimary cell index according to the received message and initiatingrandom access to the second primary cell.

In an embodiment, the means for performing the primary cell change basedon the information includes means for, in response to it being detectedthat the index (indices) of one or more of the second primary cell andsecondary cells in the second group of secondary cells included in themessage are the same as the first primary cell and secondary cells inthe first group of secondary cells while the index of the second primarycell is not same as index of any one of the secondary cells in the firstgroup of secondary cells, updating the second primary cell indexaccording to the received message, initiating random access to thesecond primary cell and continuing data transmission and or reception onthe one or more secondary cells of the first group of secondary cellswhose index (indices) is the same as any one secondary cell of thesecond group of secondary cells between the terminal device and thenetwork device.

In an embodiment, the means for performing the primary cell change basedon the information includes means for, in response to it being detectedthat the index of the second primary cell is same as index of any one ofthe first group of secondary cells, updating the second primary cellindex according to the received message and continuing data transmissionand or reception on the one or more secondary cells of the first groupof secondary cells whose index (indices) is the same as any one of thesecond primary cell and secondary cell of the second group of secondarycells between the terminal device and the network device.

FIG. 8 shows a simplified block diagram of a device 800 that is suitablefor implementing embodiments of the present disclosure. It would beappreciated that the device 800 may be implemented as at least a partof, for example, the network device 110 or the terminal device 120.

As shown, the device 800 includes a communicating means 830 and aprocessing means 850. The processing means 850 includes a data processor(DP) 810, a memory (MEM) 820 coupled to the DP 810. The communicatingmeans 830 is coupled to the DP 810 in the processing means 850. The MEM820 stores a program (PROG) 840. The communicating means 830 is forcommunications with other devices, which may be implemented as atransceiver for transmitting/receiving signals.

In some embodiments where the device 800 acts as a network device, theprocessing means 850 may be configured to configure a message indicatinga primary cell change based on the detecting by the detecting unit; andthe communicating means 930 may be configured to transmit the messageindicating a primary cell change. In some other embodiments where thedevice 800 acts as a terminal device, the processing means 850 may beconfigured to detect information of the primary cell change, and thecommunicating means 830 may be configured to receive a messageindicating a primary cell change.

The PROG 840 is assumed to include program instructions that, whenexecuted by the associated DP 810, enable the device 800 to operate inaccordance with the embodiments of the present disclosure, as discussedherein with the method 200, 300 or 400. The embodiments herein may beimplemented by computer software executable by the DP 810 of the device800, or by hardware, or by a combination of software and hardware. Acombination of the data processor 810 and MEM 820 may form processingmeans 850 adapted to implement various embodiments of the presentdisclosure.

The MEM 820 may be of any type suitable to the local technicalenvironment and may be implemented using any suitable data storagetechnology, such as semiconductor based memory devices, magnetic memorydevices and systems, optical memory devices and systems, fixed memoryand removable memory, as non-limiting examples. While only one MEM isshown in the device 800, there may be several physically distinct memorymodules in the device 800. The DP 810 may be of any type suitable to thelocal technical environment, and may include one or more of generalpurpose computers, special purpose computers, microprocessors, digitalsignal processors (DSPs) and processors based on multicore processorarchitecture, as non-limiting examples. The device 800 may have multipleprocessors, such as an application specific integrated circuit chip thatis slaved in time to a clock which synchronizes the main processor.

Generally, various embodiments of the present disclosure may beimplemented in hardware or special purpose circuits, software, logic orany combination thereof. Some aspects may be implemented in hardware,while other aspects may be implemented in firmware or software which maybe executed by a controller, microprocessor or other computing device.While various aspects of embodiments of the present disclosure areillustrated and described as block diagrams, flowcharts, or using someother pictorial representation, it will be appreciated that the blocks,apparatus, systems, techniques or methods described herein may beimplemented in, as non-limiting examples, hardware, software, firmware,special purpose circuits or logic, general purpose hardware orcontroller or other computing devices, or some combination thereof.

By way of example, embodiments of the present disclosure can bedescribed in the general context of machine-executable instructions,such as those included in program modules, being executed in a device ona target real or virtual processor. Generally, program modules includeroutines, programs, libraries, objects, classes, components, datastructures, or the like that perform particular tasks or implementparticular abstract data types. The functionality of the program modulesmay be combined or split between program modules as desired in variousembodiments. Machine-executable instructions for program modules may beexecuted within a local or distributed device. In a distributed device,program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may bewritten in any combination of one or more programming languages. Theseprogram codes may be provided to a processor or controller of a generalpurpose computer, special purpose computer, or other programmable dataprocessing apparatus, such that the program codes, when executed by theprocessor or controller, cause the functions/operations specified in theflowcharts and/or block diagrams to be implemented. The program code mayexecute entirely on a machine, partly on the machine, as a stand-alonesoftware package, partly on the machine and partly on a remote machineor entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium,which may be any tangible medium that may contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device. The machine readable medium may be a machinereadable signal medium or a machine readable storage medium. The machinereadable medium may include but not limited to an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatus,or device, or any suitable combination of the foregoing. More specificexamples of the machine readable storage medium would include anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing.

In the context of this disclosure, the device may be implemented in thegeneral context of computer system-executable instructions, such asprogram modules, being executed by a computer system. Generally, programmodules may include routines, programs, objects, components, logic, datastructures, and so on that perform particular tasks or implementparticular abstract data types. The device may be practiced indistributed cloud computing environments where tasks are performed byremote processing devices that are linked through a communicationsnetwork. In a distributed cloud computing environment, program modulesmay be located in both local and remote computer system storage mediaincluding memory storage devices.

Further, while operations are depicted in a particular order, thisshould not be understood as requiring that such operations be performedin the particular order shown or in sequential order, or that allillustrated operations be performed, to achieve desirable results. Incertain circumstances, multitasking and parallel processing may beadvantageous. Likewise, while several specific implementation detailsare contained in the above discussions, these should not be construed aslimitations on the scope of the present disclosure, but rather asdescriptions of features that may be specific to particular embodiments.Certain features that are described in the context of separateembodiments may also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment may also be implemented in multipleembodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specificto structural features and/or methodological acts, it is to beunderstood that the present disclosure defined in the appended claims isnot necessarily limited to the specific features or acts describedabove. Rather, the specific features and acts described above aredisclosed as example forms of implementing the claims.

1-16. (canceled)
 17. A method implemented at a terminal device,comprising: receiving a message transmitted from a network device, themessage being configured by detecting, for a primary cell change for theterminal device, at least one of whether layer 2 context is being kept,and one or more serving secondary cells remain; obtaining information ofthe primary cell change from the received message; and performing theprimary cell change based on the information.
 18. The method accordingto claim 17, wherein detecting whether the layer 2 context is being keptfor the primary cell change for the terminal device is detecting whethera part or entirety of the layer 2 context corresponding to a secondprimary cell keeps the same comparing to that of a first primary cell;and/or detecting the one or more serving secondary cells remaining forthe primary cell change for the terminal device is detecting whether anindex of the second primary cell is same as that of one secondary cellof a first group of secondary cells, or an index of one or more of thesecond primary cell and secondary cells in the second group of secondarycells included in the message is the same as that of one or more of thefirst primary cell and secondary cells in the first group of secondarycells; and the terminal device is being served by the first primary celland the first group of secondary cells, and the terminal device to beserved by the second primary cell and the second group of secondarycells after the primary cell change.
 19. The method according to claim18, further comprising: in response to detection that the receivedmessage includes an information element for derivation of a new securitykey, updating a second primary cell index according to the receivedmessage; deriving the new security key; resetting medium access control(MAC); re-establishing packet data convergence protocol/radio linkcontrol (PDCP/RLC); and initiating random access to the second primarycell.
 20. The method according to claim 18, further comprising: inresponse to detection that the received message includes an informationelement to trigger reconfiguring of radio link control/medium accesscontrol (RLC/MAC), updating a second primary cell index according to thereceived message; resetting medium access control (MAC); re-establishingradio link control (RLC); and initiating random access to the secondprimary cell.
 21. The method according to claim 18, further comprising:in response to detection that the received message does not include aninformation element for derivation of a new security key or triggeringreconfiguring of radio link control/medium access control (RLC/MAC)while an index of any of the second primary cell and secondary cells inthe second group of secondary cells included in the message is not thesame as that of one of the first primary cell and secondary cells in thefirst group of secondary cells, updating a second primary cell indexaccording to the received message; and initiating random access to thesecond primary cell.
 22. The method according to claim 18, furthercomprising; in response to the index of one or more of the secondprimary cell and secondary cells in the second group of secondary cellsincluded in the message is the same as that of the first primary celland secondary cells in the first group of secondary cells while theindex of the second primary cell is not same as the index of any one ofthe secondary cells in the first group of secondary cells, updating asecond primary cell index according to the received message; initiatingrandom access to the second primary cell; and continuing datatransmission and or reception on the one or more secondary cells of thefirst group of secondary cells whose index is the same as any onesecondary cell of the second group of secondary cells between theterminal device and the network device.
 23. The method according toclaim 18, further comprising; in response to a detection that an indexof the second primary cell is same as that of any one of the secondarycells in the first group of secondary cells, updating a second primarycell index according to the received message; and continuing datatransmission and/or reception on the one or more secondary cells of thefirst group of secondary cells whose index is the same as any one of thesecond primary cell and secondary cell of the second group of secondarycells between the terminal device and the network device.
 24. A terminaldevice, comprising: a non-transitory machine readable storage medium tostore instructions; and a data processor coupled with the non-transitorymachine readable storage medium to process the stored instructions to:receive a message transmitted from a network device, the message beingconfigured by detecting, for a primary cell change for the terminaldevice, at least one of whether layer 2 context is being kept and one ormore serving secondary cells remain, obtain information of the primarycell change from the received message, and perform the primary cellchange based on the information.
 25. The terminal device according toclaim 24, wherein the detection of whether the layer 2 context is beingkept for the primary cell change for the terminal device is detectingwhether a part or entirety of the layer 2 context corresponding to asecond primary cell keep the same comparing to that of a first primarycell; and/or the detection of the one or more serving secondary cellsremaining for the primary cell change for the terminal device isdetecting whether an index of the second primary cell is same as that ofone secondary cell of a first group of secondary cells, or an index ofone or more of the second primary cell and secondary cells in the secondgroup of secondary cells included in the message is the same as that ofone or more of the first primary cell and secondary cells in the firstgroup of secondary cells; and the terminal device is being served by thefirst primary cell and the first group of secondary cells, and theterminal device to be served by the second primary cell and the secondgroup of secondary cells after the primary cell change.
 26. The terminaldevice according to claim 25, the terminal device is further to: judgewhether the received message includes an information element forderivation of a new security key; or judge whether the received messageincludes an information element to trigger reconfiguring of radio linkcontrol/medium access control (RLC/MAC); or judge whether the index ofany of the second primary cell and the second group of secondary cellsincluded in the message is the same as the first primary cell and thesecond of group secondary cells; or judge whether the index of thesecond primary cell included in the message is same as index of any oneof the first group of secondary cells.
 27. The terminal device accordingto claim 25, wherein the terminal device is further to: a detection thatthe received message includes an information element for derivation of anew security key, derive a second security key, reset medium accesscontrol (MAC), re-establish packet data convergence protocol/radio linkcontrol (PDCP/RLC) and initiate random access to the second primarycell.
 28. The terminal device according to claim 25, wherein theterminal device is further to: in response to a detection that thereceived message includes an information element to triggerreconfiguring of radio link control/medium access control (RLC/MAC),update a second primary cell index according to the received message,reset medium access control (MAC), re-establish radio link control (RLC)and initiate random access to the second primary cell.
 29. The terminaldevice according to claim 25, wherein the terminal device is further to:in response to the received message does not include an informationelement for derivation of a new security key or trigger reconfiguring ofradio link control/medium access control (RLC/MAC) while the index ofany of the second primary cell and the second group of secondary cellsincluded in the message is not the same as that of the first primarycell and the second group of secondary cells, update a second primarycell index according to the received message and initiate random accessto the second primary cell.
 30. The terminal device according to claim25, wherein the terminal device is further: in response to a detectionthat the index of one or more of the second primary cell and secondarycells in the second group of secondary cells included in the message isthe same as that of the first primary cell and secondary cells in thefirst group of secondary cells while the index of the second primarycell is not same as an index of any one of the secondary cells in thefirst group of secondary cells, update a second primary cell indexaccording to the received message, initiate random access to the secondprimary cell and continue data transmission and/or reception on the oneor more secondary cells of the first group of secondary cells whoseindex is the same as any one secondary cell of the second group ofsecondary cells between the terminal device and the network device. 31.The terminal device according to claim 25, wherein the terminal deviceis further to: in response to a detection that the index of the secondprimary cell is same as an index of any one of the first group ofsecondary cells, update a second primary cell index according to thereceived message and continue data transmission and/or reception on theone or more secondary cells of the first group of secondary cells whoseindex is the same as that of any one of the second primary cell andsecondary cell of the second group of secondary cells between theterminal device and the network device. 32-35. (cance